Centrifugal ball peening machine



May 16, 1950 `R. D. HAwoRTH, JR., ErAL 2,503,333

' CENTRIFUGAL BALL -PEENING MACHINE Filed Aug. 4, 1947 Patented May 16, 195o CENTRIFUGAL BAEL PEENING MACHINE Roy D. Haworth, Jr., Chicago, and William E.

Mahin, La Grange, Ill., assignors, by mesne assignments, to Michiana. Products Corporation, Michigan City, Ind., a corporation of Indiana Application August 4, 1947, Serial No. 765,868

2 Claims. (C1. 51-9) Centrifugal abrasive throwing or ball peening machines usually include a wheel or rotor about inches in diameter having spaced disks with a plurality of substantially radial blades between them, each having along its leading face a propelling surface for abrasive or balls, as may be illustrated by the following patents: Unger, 2,162,139, June 13, 1939; Turnbull, 2,204,633, June 18, 1940; Turnbull, 2,204,634, June 18, 1940; Turnbull, 2,306,847, Dec. 29, 1942; and Unger, 2,376,639, May 22, 1945.

In use, those machines operate at a speed on the order of 2,000 to 2,500 R.P.M., and the outer ends of the blades are subjected to a violet beating by abrasive or shot rebounding from the work piece under treatment (Turnbull 2,306,847, December 29, 1942, and Unger 2,376,639, May 22, 1945) with the result that the outer end portions of the blades chip and progressively crack and frequently fail at less than thirty hours service. The percentage of failure increases, generally, when the blades are made of alloy materials providing high resistance to wear or abrasion by the movement of the shot over the propelling surface.

Many expedients have been tried to prevent or retard this destruction, but, at most, with only qualif-led success.

The principal object of this invention is to prevent the destructive action on such blades, and thus increase their useful life.

Generally speaking, this is accomplished by removing the corners at the outer ends of each blade and curving the outer end portions away from the leading face of the blade so as the present a smooth curved surface to the rebounding abrasive or shot.

A further desirable improvement is made by adding a strengthening bead along the trailing corner of the outer end of each blade.

In the drawings, Fig. 1 is a vertical section through a conventional centrifugal ball peening machine, shown somewhat diagrammatically;

Fig. 2 is a perspective view looking at the leading face of the improved blade;

Fig. 3 is a similar view looking at the trailing face of the improved blade; and

Fig. 4 is a longitudinal section taken on the line 4 4 of Fig. 2.

The machine shown in Fig. 1 includes a rotor having spaced disks I0 and ,Il provided with radial grooves I2receivingA the marginal portions of the throwing blades I3, which are made fast against outward movement by cap screws I4, entering specially prepared sockets in the trailing face of the blades, as is well known.

In use, the shot is supplied through a spout I5 to an impeller I 6, which distributes them thr gh an opening I1 in a control sleeve I8 and int the path of the blades I3, which propel them outwardly at a high rate of speed by travel along the leading face of each of the blades.

The outer end faces of each-of the blades in the conventional machine are fiat and at right angles to the length of the blade, as may be seen from the patent to Unger No. 2,376,639, May 22, 1945, and Turnbull No. 2,306,847, December 29, 1942. Some of the shot striking the work piece rebounds to impact with the end portions of the propelling blades, apparently at the leading corner or adjacent thereto, with a violence that is a resultant of the hig-h speed of the blade and the high speed of the rebounding shot. This action produces a chipping and cracking which develops as a type of fatigue fracture, and eventually the blade fails. Tests run for the purpose indicate that the failure at about 30 hours service, or less. is in excess of 25%.

It has been found that removingl the square corner at the outer end of the blade on the leading face and curving the blade away from the leading face I9, as indicated at 20 in Fig. 2, reduces the dama-ge to a fairly negligible amount. The empirical data seem to justify the statement that the surface of the leading face I9 and the side anges 2I should be blended into a rounding or curving surface leading to the end 22 of the blade, without any abrupt change in surface. No exact curvature can be specified, but, with blades 71/8" long of the conventional design, the curvature shown in Figs. 2 and 4 is satisfactory.

, An additional improvement is made by addinga rounded bead 23 on the trailing side at the end of the blade, as shown in Figs. 2, 3, and 4, and inclining the bead inwardly substantially as indicated at 24 in Fig. 4.

` These improvements can be made in conventional blades without changing the length, thickness, or the thickness of the ilanges 2| so that the new blades can be used in the great number of throwing machines already in service.

The blades are very conveniently produced by casting in an alloy offering appropriate resistance to the abrasive action of the shot as they are propelled along the leading face of the blades.

Preferably, the blade should be made of an alloy containing 8% to 16% chromium, 1% to 4% molybdenum, and 11A-1% to 4% carbon, the principal remainder iron, because this alloy has such a high resistance to the abrasive action of the shot on the propelling face of the blades. But the use of the rounding with or without the strengthening bead gives the mentioned advantages with other materials. In this connection, the rounding is also applied to the corners 25 and 26.

We claim:

1. A blade for centrifugal abrasive throwing wheels which include a rotor adapted to be driven at high speed and carrying a plurality of substantially radially extending blades, said blade having a surface along the leading side on which said abrasive is propelled and a trailing side opposite said leading side, and having a curved surface merging the leading side and the trailing side into its outer end and presented to the abrasive rebounding from the work.

2. A blade for centrifugal abrasive throwing Wheels which include a rotor adapted to be driven at high speed and carrying a plurality of substantially radially extending blades, said blade having a surface along the leading side on which said abrasive is propelled and a trailing side opposite 4 said leading side and having a. curved surface merging the leading side into its outer end and presented to the abrasive rebounding from the work, and a strengthening bead at its outer end and rounded to form with said curved surface a continuous curved face about the entire end of said blade.

ROY D. HAWORTH, JR. WILLIAM E. MAHIN.

REFERENCES CITED The following references are of record in the -le of this patent:

UNITED STATES PATENTS 

